The removal of water from a hole drilled deep into the ground, can be accomplished by the use of an air lift incorporated in the drill bit. The drill string may include a plurality of concentric pipes, most generally two concentric pipes are utilized in an arrangement known as a "dual string." During the drilling operation, drilling mud is pumped down through either the space between the pipes to the drill bit and the mud and entrained bits of rock flow upwardly through the inner pipe, or vice versa. When pumping out water, compressed air can be pumped down one of these spaces to force water through a coupling at the drill bit into the other space, the compressed air being utilized to lift the water up to the surface of the earth. However, it is found that this procedure becomes ineffective when only a moderate level of water is left in the hole, such as when about 40 to 50 feet of water remains. This fluid can be removed by a bailer, which includes a bucket with a check valve added at the bottom, but this technique is cumbersome.
One technique for removing substantially all of the water from a deep well involves the use of an electrically powered pump. However, the use of electrically powered apparatus requires that a crew of electricians be utilized, instead of just the drill crew which is more familiar with mechanical apparatus. Also electrically operated motors at the bottom of a deep well are not highly reliable, since the motor and all electrical connections, as well as cables leading through the drill string to the motor, must be isolated from the water, and rock bits can cause damage to insulation.
One object of the present invention is to provide a relatively simple and reliable pumping apparatus which can remove fluid, such as water with entrained mud and rock bits, from the deepest portion of a well.
Another object is to provide a dewatering pump for use in a deep well, which normally can be operated by the same crew members utilized to drill the well, and who may be proficient in only mechanical and hydraulic technologies.
An additional object is to provide a simple and reliable pumping apparatus in the form of a self contained subassembly that can be readily attached to the bottom of the dual string which is utilized to drill the hole.